Early Limnology:
Temperature
Profiles
Lake
Zones
Zones are dynamic!
Input of heat

Mixing forces
The stratification and mixing
cycle of an average-sized,
temperate lake
Stratification and Mixing
Stratification and Mixing
Stratification and Mixing
Stratification and Mixing
Stratification and Mixing
The Whole Cycle in One
Confusing Figure!
Factors that influence
stratification pattern
• Heating / Density  Wind / Waves
• Depth
• Surface Area
• Topography / Location / Exposure
Temperature
The Family of Lake Cycles
Incident Solar Radiation
The Family of Lake Cycles
Amictic
• Perennially ice-covered
• Inversely stratified
The Family of Lake Cycles
Cold Monomictic
• Water temperature never exceeds 4C
• Ice-covered for most of the year =
inversely stratified
• One period of free circulation in summer
at or below 4C
The Family of Lake Cycles
Dimictic
The Family of Lake Cycles
Warm Monomictic
•
•
•
Circulates once in winter at or above 4C
Directly stratified for the rest of the year
Not ice covered
The Family of Lake Cycles
Oligomictic
• Stable, direct stratification most of the
year
• Circulation at irregular intervals (scale of
years) during cool periods
The Family of Lake Cycles
Polymictic
•
Frequent periods of mixing per year
•
Not ice-covered
Cold Polymictic
•
•
•
•
Equatorial, high elevation
Hovering around 4C
Intense heat during day (stratification)
Intense cooling at night (mixing)
Warm Polymictic
• Warm throughout (i.e., well above 4C)
• Sometimes get intense heating of
epilimnion = development of weak
stratification.
4C is IMPORTANT
Holomixis: Circulation occurs
throughout the entire water
column.
Meromixis: Primary water
mass never mixes with the
lower portion.
Stratification in meromictic lakes
•
Monimolimnion: deep stratum, high
salinity
•
Chemolimnion: strong salinity gradient
•
Mixolimnion: upper stratum (i.e., epi-,
meta-, and hypolimnion)
How does the salt get there?
•
Ectogenic meromixis
•
Crenogenic meromixis
•
Biogenic meromixis
Consequences of meromixis
•
Monimolimnion = Dead Zone
•
Chemolimnion = Heat Trap
Wavelength
Frequency
More Blue
More Red
Consequences of meromixis
•
•
•
•
Hot Lake, north-central WA
On top of epsom salt excavation
High MgSO4 in monimolimnion
Temperature in monimolimnion
can get to 50C!
Why Lake Circulation Matters:
Lake Nyos Gas Disaster
Lake Nyos Degassing Project
• Pipe is 203 m long and
14.5 cm in diameter.
• Upper end attached to
raft and supported by
lines to shore.
• Oxygen
• Light
• Temperature
Patterns along the
“river continuum”
• Oxygen
• Light
• Temperature
Temperature along streams
Temperature fluctuations along the
streams
Effect of Groundwater on Stream Temperature:
Nyack Floodplain, MT
Oxygen along streams
• DO in unpolluted, flowing water usually
at or near saturation, and concentrations
are of little biological significance.